[sdiy] Integral scope on VCO

[Thomas Dunker]

On Wed, 14 Apr 2004, Harry Bissell Jr wrote:

> I would NOT try the scope in a VCO project. Keeping
> the
> EMI from the scope from interfering with the VCO will
> be the major design challenge.

 You really think so? Anything going on in the VCO is at ultra low
impedances compared to the CRT and the deflection amps. In any case
there's not much of a magnetic field to worry about (I'd worry more about
the fields from the HV power supply transformer affecting the CRT...)
and the CRT can be shielded easily from the electrostatic fields.
 Even in precision oscilloscopes there's always a mumetal shield around
the CRT - to keep magnetic fields in the rest of the instrument from
distorting the beam deflection in the CRT.

 I'll probably wire a prototype for the basic scope PSU and drivers (and
the CRT itself) anyway and see if I can provoke it to interfere with the VCO
when brought into close proximity. That will certainly settle the question...

 What kind of interference scenario do you picture anyway.

Thomas